In general, an orthodontic treatment for correcting a tooth carried out in a dental clinic is a series of procedures of dealing with prevention and correction of functional disorder caused due to irregularities of the teeth-generally entailing the straightening of crooked tooth or the correcting of a poor bite, or malocclusion (physiologically unacceptable contact of opposing dentition) and of esthetic disorder generally entailing the correcting of a protruding chin, a snaggletooth, an inturned tooth, or the likes.
The correcting treatment includes the steps of manufacturing a plaster cast of a patient's teeth at a point of initializing the treatment and measuring a configuration data, such as a location of the tooth, a gradient of the tooth, and the likes, determining a proper method for correcting the irregular teeth into regular teeth, and mounting a bracket for correction. However, the conventional method has a drawback in measuring the configuration data since the 3-dimension (3D) configuration data including the tooth location and gradient are manually measured, thereby deteriorating accuracy and consuming lots of time and labor. In addition, the conventional method requires a large storage space and careful maintenance since a lot of plaster casts should be stored until the correcting treatment finishes.
To solve the aforesaid problems, there is suggested a 3D scanning system which can 3D scan a plaster model for a computer modeling, extract a 3D configuration data on a computer, and store the plaster model in a computer data form.
In contrast to the conventional method in which the tooth plaster model is manually measured for dental correction, the 3D scanning system uses a 3D-coordinate measuring system in a manner that a plaster model is analyzed and data is processed in a computer, so that the configuration data necessary for the dental correction can be exactly measured in a shorter time.
For this, it is required a technology, which is capable of accurately measuring the plaster model and enabling a real value to become the same as a measured value, such as acquisition of image, removal of error and noise and conversion of data, and a surface generation technology, namely a mesh and a curved surface generation technology, which is capable of generating a surface of an object by using a point data to measure the configuration data of the tooth model using a 3D point data obtained by the measurement.
The configuration created on the computer in this manner is useful for many fields in next studies as well as dental correction. Meanwhile, the tooth plaster model which becomes the object to be measured for the dental correction is very complex in shape and very rough on surface thereof. In addition, the plaster model is almost uniform in its overall shape and size and uniform in its quality and color. In measuring the tooth plaster model having the aforementioned characteristics, there are parts which are important to the orthodontic treatment and other parts which are not important. It is desirable that a measuring time is the shortest possible and input of dentists is minimized until a result is obtained.
Further, as for the measurement result, a measure accuracy is high enough to be used for medical treatment purpose, locations and intervals of measurement points are selectable to generate the tooth model in computer graphics, and the configuration data for medical use is extracted from the measurement points.
An existing 3D scanner is divided into a non-contact 3D scanner and a contact 3D scanner. The existing 3D scanner has the following features and problems in measuring the tooth plaster model having the above characteristics.
1. Non-contact 3D Scanner
The non-contact 3D scanner is classified into a scanner which linearly drives a laser distance sensor in three directions, and a scanner which uses a laser slit and a camera. The 3D scanner using the laser distance sensor is difficult to measure a vertical plane or a surface which fronts to the bottom. Therefore, a physical position of the object should be changed, the origin should be defined again and the object should be measured again, such that a measuring time is extended and a skillful technology is required. Further, a Z-axis should be moved along the shape of the object and an expensive reverse engineering program is required to extract the configuration data necessary for the orthodontic treatment.
The scanner using the laser slit and camera is capable of performing a linear movement of one degree of freedom. However, this scanner disadvantageously generates a portion which is not able to be measured since when an object has a complex shape, a range of vision of the camera is hidden by the shape of the object itself, and the scanner requires the expensive reverse engineering program to extract the configuration data necessary for the orthodontic treatment.
2. Contact 3D Scanner
The contact 3D scanner obtains a 3D coordinate of a contact point by linearly moving a probe in three directions and contacting the same to an object. This scanner can't measure a curvature more minute than the probe in size and has a difficulty in measuring a downward-facing surface. When measuring the downward-facing surface, the scanner changes a position of the object, defines the origin again, measures the object again. Accordingly, an operator should move the probe in person to measure the downward-facing surface, thereby extending a measuring time and requiring a skillful technology. Additionally, the equipment is high priced and the expensive reverse engineering program should be used to extract the configuration data for the medical purpose.
As stated above, both the conventional non-contact and contact 3D scanners for measuring the tooth plaster model have drawbacks in that the complex-shaped model is difficult to be measured, the skillful measuring technology is required and the expensive reverse engineering program is required to extract the configuration data.